Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$249.37	5.458%	$262.9806	$262.98	$263.00	$263.00
Purchase #2	$151.40	9.359%	$165.5695	$165.57	$165.55	$165.60
Purchase #3	$5.80	5.840%	$6.1387	$6.14	$6.15	$6.10
Purchase #4	$133.66	7.670%	$143.9117	$143.91	$143.90	$143.90
Purchase #5	$18.52	9.467%	$20.2733	$20.27	$20.25	$20.30
Purchase #6	$11.89	4.472%	$12.4217	$12.42	$12.40	$12.40
Purchase #7	$176.36	13.738%	$200.5883	$200.59	$200.60	$200.60
7 purchase totals =	$747.00		$811.8838	$811.88	$811.85	$811.90